1. Field of the Invention
The present invention relates to the fabrication of integrated circuits. More particularly, the invention relates to removal of processed silicon wafers from a plasma reactor.
2. Background of the Invention
One of the primary steps in the fabrication of modem semiconductor devices is the formation of a thin film on a semiconductor substrate by chemical reaction of gases. Such a deposition process is referred to as chemical vapor deposition or CVD. Conventional thermal CVD processes supply reactive gases to the substrate surface where heat-induced chemical reactions take place to produce a desired film. The high temperatures at which some thermal CVD processes operate can damage device structures having metal layers previously formed thereon.
Other CVD methods of depositing silicon oxide layers over metal layers at relatively low temperatures include plasma-enhanced CVD (PECVD) techniques such as described in U.S. Pat. No. 5,362,526. Plasma-enhanced CVD techniques promote excitation and/or disassociation of the reactant gases by the application of radio frequency (RF) energy to a reaction zone near the substrate surface, thereby creating a plasma of highly reactive species. The high reactivity of the released species reduces the energy required for a chemical reaction to take place, and thus lowers the required temperature for such PECVD processes.
Deposition of dielectric layers using PECVD methods typically leaves a negative charge on the silicon wafer. When the dielectric layer is the final layer to be deposited in a plasma chamber, the negative charge on the wafer binds the wafer to the susceptor or substrate support plate. Lifting of the wafer may require sufficient force to break the wafer and has resulted in a procedure which neutralizes the wafer. After deposition of the dielectric layer, an oxygen plasma has been used to purge the plasma chamber and generate sufficient positive species to neutralize the wafer. The method relies on a low energy plasma as a result of oxygen in the plasma and does not always produce sufficient positive species to neutralize the wafer.
There remains a need for a process for neutralizing charged wafers to assist in removal of the wafers from a plasma chamber. It is an object of this invention to provide such a method and an integrated apparatus for performing the method.